There's no polarity in light bulbs. They are essentially fuses that just quite can't *pop* due to the bulb housing. They glow because the wire/filament inside is being overheated. Just like a blade fuse, they don't care which way the current flows through them. You can install fuses in direction you want, right? It's the same for this. Also consider single element bulbs like 1156's for example. There is no directionality to them when popping them into their sockets.
When dealing with DC voltage, motors are about the only thing that cares about polarity. If you reverse a motors polarity,you reverse the direction that it will spin. It won't hurt it at all, but you don't want your engine cranking backwards, for example.
Yeah, it seems odd in a way, but you're correct. Bulbs are not sensitive to polarity.